1. Field of the Invention
The present invention relates to a reflector by which the optical path of light incident on one of side surfaces of a liquid-crystal display device is changed to a viewing direction efficiently, and with which it is possible to form a lighting-external light double mode liquid-crystal display device which is small in thickness, light in weight, bright and easy to view.
The present application is based on Japanese Patent Application No. 2000-34958, which is incorporated herein by reference.
2. Description of the Related Art
Greater reduction in thickness, size and weight of lighting-external light double mode liquid-crystal display devices has been demanded for the purpose of reduction in size and weight of portable personal computers and portable telephone sets, etc. In the mean while, it is difficult to reduce thickness, size and weight of a liquid-crystal display device provided with a front-lighting system using a background-art side-lighting type light pipe, because the light pipe needs to have a thickness of not smaller than 1 mm under the necessity of light transmission. The same difficulty is also applied to a liquid-crystal display device provided with a back-lighting system using a half-transmission type reflector because the device also uses such a side-lighting type light pipe which needs a considerable thickness.
In addition, in the case of a back-lighting system using a half-transmission type reflector, the addition of the half-transmission type reflector makes the volume and weight of the liquid-crystal display device larger. Moreover, light is diverged into transmitted light and reflected light by the half-transmission type reflector. There is there fore a problem that not only viewing in a lighting mode but also viewing in an external light mode becomes dark so that brightness of the display device using the half-transmission type reflector is inferior to that of a reflection exclusive type liquid-crystal display device using a high-reflectance reflection layer. Moreover, it is necessary to provide a gap between the light pipe and the liquid-crystal panel. This, as well as addition of a gap retaining mechanism, makes the volume and weight of the liquid-crystal display device larger.